Influence of gonadal steroids on susceptibility to Brugia malayi in scid mice.

In the present study, we demonstrate that male scid/scid mice have higher adult worm burdens than do female scid/scid mice following equal challenge doses of infective Brugia malayi L3 larvae. Gonadectomy of four week old immature mice has no effect on worm burden in either sex, suggesting that the gender dichotomy between males and females does not depend on continued presence of endogenous gonadal steroids. The worm yield from female, but not male, mice can be increased by prepubertal oophorectomy combined with administration of either estradiol or testosterone in depot form. Our results raise the possibility that prepubertal steroid pulse(s) result(s) in physiological changes in male scid/scid mice that enhance worm growth. These studies confirm earlier reports of epidemiological data in humans suggesting a sexual dimorphism in susceptibility to filarial infection. Our data suggest that this gender difference is not due simply to the presence of adult gonadal steroids, but rather to ontogenic differentiative actions of sex steroids in the host.